1. Field of the Invention
The present invention relates to telecommunications, and more particularly, to an method for applying time-shifting functionality to voice communications.
2. Description of Related Art
Voice communication systems consist of one of more “channels.” In the case of Push To Talk (PTT) systems, such as tactical radios or PTT over Cellular (PoC), only a single channel is used whenever someone is transmitting. A user cannot transmit while their device is receiving. These systems are said to be “half-duplex”. The alternative is “full-duplex” systems like landline telephones, cellular telephones, or VoIP systems such as Skype or SIP. Each of these full-duplex systems uses two channels, one for voice being received and the other for voice being transmitted. User communication devices generally “connect” these channels, either to a speaker, a microphone, or both, depending on the duplex and current mode of operation.
Many full-duplex telephony systems have some sort of message recording facility for unanswered calls such as voicemail. If an incoming call goes unanswered, it is redirected to a voicemail system. When the caller finishes the message, the recipient is alerted and may listen to the message. Various options exist for message delivery beyond dialing into the voicemail system, such as email or “visual voicemail,” but these delivery schemes all require the entire message to be left before the recipient can listen to the message.
Many home telephones have answering machine systems that record missed calls. They differ from voicemail in that the caller's voice is often played through a speaker on the answering machine while the message is being recorded. The called party can pick up the phone while the caller is leaving a message. If this occurs with most answering machines, the recording of the message stops while the parties engage in a telephone conversation. With other answering machines, however, the live conversation will be recorded unless the called party manually stops the recording. In either recording situation, there is no way for the called party to review the recorded message until after the recording has stopped. There is no way for the recipient to review any portion of the recorded message other than the current point of the conversation while the conversation is ongoing and is being recorded. Only after the conversation has concluded and the parties have hung up or the recipient has manually stopped the recording can the recipient go back and review the recorded message or conversation.
Some more recent call management systems provide a “virtual answering machine,” allowing callers to leave a message in a voicemail system, while giving called users the ability to hear the message as it is being left. The actual answering “machine” is typically a voicemail-style server, operated by the telephony service provider. Virtual answering machine systems differ from standard voice mail systems in that the called party may use either their phone or a computer to listen to messages as they are being left. Similar to an answering machine as described in the preceding paragraph, however, the called party can only listen at the current point of the message as it is being left. There is not way to review previous portions of the message before the message is left in its entirety and the caller hangs up.
Certain mobile phone handsets have been equipped with an “answering machine” feature inside the handset itself and that behaves similarly to a landline answering machine as described above. With these answering machines, callers may leave a voice message, which is recorded directly on the phone of the recipient. While the answering machine functionality has been integrated into the phone, all of the limitations of answering machines, as discussed above, are still present.
With current PTT systems, incoming audio is played on the device as it is received. If the user does not hear the message, for whatever reason, the message is irretrievably lost. Either the sender must resend the message or the recipient must request the sender to re-transmit message. PTT systems generally do not have any sort of “missed message” recording capability.
Other forms of PTT messaging systems exist that are purely message based and are never live. See for example U.S. Pat. No. 7,403,775 and U.S. Publications 2005/0221819 and 2005/0202807.
A problem with all the above-mentioned systems is that there is no way for: (i) a recipient of a message to review the message while it is being left; (ii) review received messages at an arbitrary time after receipt in a time-shifted or messaging mode; or (iii) seamlessly transition the exchange of messages between a sender and a recipient between the time-shifted mode and a real-time mode.